🚀 go-pugleaf

mucds@uxa.ecn.bgu.edu (Corey D. Stinson) writes:


>Recently someone posted the code below in answer to someone's questoin
>concerning loading directly into the VGA memory buffer.  The coder
>mentioned that he/she was using Microsoft C.  Neither of the examples
>below will work for me (I'm using Turbo/Borland C++) and I wonder if
>someone might have some suggestions which would allow this to work
>correctly under my compiler:

>Why this doesn't work:

>    unsigned char (far *VideoMemory)[200][320];
>    VideoMemory=(unsigned char (far *)[200][320])0xA0000000L;
>    for (x=0;x<=15;x++ )
>	for (y=0;y<=15;y++)
>	    VideoMemory[y][x]=pic[x][y];
  

  CHANGE TO: (*VideoMemory)[y][x]=pic[x][y];

>   **** LValue required error on above line ****

>    unsigned char (far *VideoMemory)[200][320];
>    VideoMemory=(unsigned char (far *)[200][320])0xA0000000L;
>    for (x=0;x<=15;x++ )
>	for (y=0;y<=15;y++)
>	    VideoMemory[y][x]=pic[x][y];

>    -A good compiler should be able to optimize this pretty good.

>    OR, using Microsoft C inline assembler, a very fast version:


>Why this doesn't work:

>   void PUTBLT( int x, int y, int width, int height, char far * buffer )
>   {
>   _asm   {
>   push   es
>   push   ds 
>   mov    ax, A000h   ; The segment of VGA memory
>   mov    es, ax
>   mov    ax, 320
>   mul    y
>   add    ax, height  ; AX = y*320+x
>   mov    di, ax      ; The offset into VGA memory
>   mov    dx, width   ; USe DX for width
>   mov    bx, height  ; Use BX for height 
>   lds    si, buffer  ; Point DS:SI to the memory

rowloop: push   di         ; << CHANGE THIS LINE!!

>   mov    cx, dx      ; Number of pixels to fill per row
>   rep    movsb       ; blast 'em out there

    pop    di          ; << ADD THIS LINE!!!
    add    di, 320     ; Move to next scan line

>   dec    bx
>   jnz    rowloop 

>*** it's not recognizing the label I designated previously.  A friend
>    tells me it is illegal to create labels in inline assembler but
>    I would think there would be a way to do it.

     ***** I'm not sure.... inline assembly does allow labels... maybe
	   check your manual for the compiler.
> **
>   pop    ds
>   pop    es
>    
>    -This is assuming you're using mode 13h.
>    -This just writes directly to video memory.

>Any help or advice would be GREATLY appreciated! :)

    Mail me if you can't get these to work.


-- 
------------------------------------------------------------------------
  John A. Slagel, email: jas37876@uxa.cso.uiuc.edu